Copper-Catalyzed C-H (Phenylsulfonyl)difluoromethylation of Acrylamides: Scope, Mechanism, and Critical Role of Additives

Herein, we report the Cu-complex catalyzed, native functional group-assisted, and TFA/NMF additives promoted (phenylsulfonyl)difluoromethylation of vinylic C(sp2)-H bond of acrylamides. Using our in-home designed reagent, this reaction enables the construction of the C(sp2)-CF2SO2Ph bond from simple C-H bond activation by copper catalysis under mild reaction conditions with total Z-selectivity. The versatility of utilized fluorinated group was illustrated by its conversion into value-added CF2 moieties as well as the remarkable =CHF residue. The performed experimental and computational mechanistic studies enabled to identify the true nature of active catalyst and substrate, as well as establish critical roles of TFA and NMF additives. In this reaction, the TFA acts as a promoter of the much-needed CuII/CuII -> CuIII/CuI disproportionation, while the NMF facilitates the following ligand exchange and C-C coupling processes. We ruled out the generation of radical intermediates and established the C-H activation to be irreversible and the rate-determining step of the entire process. We report first CuII-catalyzed Z-selective difluoromethylation of vinylic-C(sp2)-H bond of acrylamides bearing a native functional group with an in-home designed and stable electrophilic salt. The versatility of the CF2SO2Ph group was shown and mechanistic studies supported by DFT calculations highlight the critical role of additives. The process was achieved under robust reaction conditions in the presence of the readily available Cu(OAc)2.+image